1. Field of the Invention
The present invention is generally related to sensors for use in machines for washing articles and, more particularly, to a sensor platform, or duster, which contains and protects a series of parameter sensing components and is attachable in various places within a dishwasher or washing machine for monitoring the condition of the liquid used by the machine.
2. Description of the Prior Art
U.S. Pat. No. 5,140,168, which issued to King on Aug. 18, 1992, discloses a turbidimeter signal processing circuit which uses alternating light sources. The turbidimeter includes a housing which has a cavity with an inlet through which fluid flows. Two emitters are alternately driven by an alternating signal having a given frequency to transmit modulated light beams through the fluid. Two detectors produce signals representing the intensity of scattered and unscattered light within the fluid. Each of these detector signals is processed to measure the level of the signal component at the given frequency. Such processing includes filtering and phase demodulating the detector signals to produce a signal indicative of the levels of the component signals at the given frequency. The turbidity is calculated from the signal levels measured as each emitter is excited.
U.S. Pat. No. 3,888,269, which issued to Bashark on Jun. 10, 1975, describes a control system for a dishwasher. The dishwasher has a single control pushbutton adapted to perform a multiplicity of different dishwashing and dishtreating operations. It includes an improved automatic control which has the capability to determine an optimum treatment of the dishes in the dishwasher based on the condition of the dishes when they are in the dishwasher.
U.S. Pat. No. 3,870,417, which issued to Bashark on Mar. 11, 1975, discloses a sensor for a dishwasher. It describes a method and apparatus for determining the condition of a liquid, such as a dishwashing liquid, including means for determining the turbidity of the liquid and means for determining a preselected amount of evaporation of the liquid so as to determine a dryness condition. Means are provided for directing light radiation upward into the liquid and for sensing the light radiation reflected either from solids carried by the liquid to provide a turbidity determination or reflected from the underside of the upper surface of the liquid to provide a dryness determination.
U.S. Pat. No. 5,172,572, which issued to Ono on Dec. 22, 1992, discloses an automatic washing apparatus for washing dirty things in a washing tank to which washing liquid is supplied. The apparatus comprises a light emitting element for emitting light to the washing liquid which has passed through the washing tank. It also comprises a first light receiving element for receiving a linear light beam which travels through the washing liquid along the optical axis of the light emitting element. Furthermore, it comprises a second light receiving element for receiving scattered light which travels through the washing liquid in directions deviated from the optical axis of the light emitting element, wherein washing conditions are controlled in accordance with the quantity of light received by the first light receiving element and the quantity of light received by the second light receiving element.
U.S. Pat. No. 3,662,186, which issued to Karklys on May 9, 1972, describes an electronic control circuit for appliances. The control for a multiple function apparatus, such as an appliance, utilizes an electronic clock, or timer, electronic program circuitry and digital circuitry to select and control the functions to be performed. The electronic program circuitry has a plurality of bi-stable circuits, one portion controlling a series of steps repeated in each of several subcycles and the other portion controlling the sequence of subcycles. The second portion may be preset to establish a desired operating program. The digital circuitry is responsive to the condition of the bistable program circuits and to the clock to control the operation of the appliance.
U.S. Pat. No. 5,291,626, which issued to Molnar et al on Mar. 8, 1994, discloses a machine for cleansing articles. The machine, such as a dishwasher, incorporates a device for measuring the turbidity of at least partially transparent liquid. The device includes a sensor for detecting scattered electromagnetic radiation, regardless of polarization, and a sensor for detecting transmitted electromagnetic radiation.
U.S. patent application Ser. No. 08/053,042 which was filed by Kubisiak et al on Apr. 26, 1993 and assigned to the assignee of the present application describes a turbidity sensor that is provided with a light source and a plurality of light sensitive components which are disposed proximate a conduit to measure the light intensity directly across the conduit from the light source and at an angle therefrom. The conduit is provided with a plurality of protrusions extending radially inward from the walls of the conduit to discourage the passage of the air bubbles through the light beam of the sensor. The direct light beam and scattered light are compared to form a relationship that is indicative of the turbidity of the liquid passing through the conduit. The rate of change of turbidity is provided as a monitored variable. The technique referred to as the delta-sigma analog-to-digital conversion method is described in significant detail in the Kubisiak et al application. The Kubisiak et al application described above is expressly incorporated by reference herein.
U.S. Pat. No. 4,906,101, which issued to Lin et al on Mar. 6. 1950, describes a turbidity measuring device for measuring turbidity in static or dynamic streams, wherein the fluid has up to 8,500 ppm solids and at a depth of up to 8 inches. The device contains a high intensity light source, a means for controlling the wavelength of the transmitted light to between 550-900 nm to filter color variables in the stream. It also comprises a photosensor that is aligned with the viewing means for picking up the light transmitted through the streams.
U.S. Pat. No. 5,048,139, which issued to Matsumi et al on Sep. 17, 1991, discloses a washing machine with a turbidimeter and a method of operating the turbidimeter. The machine uses a turbidimeter to measure turbidity of cleaning water for controlling the duration of its washing and cleaning cycles. Quality of this control is improved by taking measurements when the water flow is weak so that the effects of foams are negligible and waiting until turbidity drops at the beginning of the cycle to detect the initial value used in subsequent steps.
U.S. Pat. No. 4,999,514, which issued to Silveston on Mar. 12, 1991, discloses a turbidity meter with parameter selection and weighting. The meter has a sensory unit which is supported in a fluid under test with a light source and at least two light sensors supported so that one light sensor is in line with the source to receive transmitted light and the remaining sensor or sensors are arranged to receive light that is scattered by the fluid. Both the source and the sensors have flow forming chambers connected to a source of pressurized fluids so that a thin layer of this fluid is caused to flow over lenses of the source and sensors to prevent deposition of material from the fluid under test.
U.S. Pat. No. 4,619,530, which issued to Meserol et al on Oct. 28, 1986, describes a cuvette with an integral optical elements and electrical circuit with photoemissive and photosensitive elements in intimate optical contact with the optical elements. The combination of a cuvette for receiving a medium undergoing change in optical characteristics which change modifies the energy level of array of energy passing through the medium and wherein the cuvette is provided with integrally formed first and second array modifying optical means such as collimating and collecting lens. The first ray modifying optical means receives and modifies the ray in a first manner, such as by collimation, and them transmits the ray into the medium. The second ray modifying optical means receives and modifies the ray in a second manner, such as by collection, upon the ray passing through the medium and transmits the ray from the cuvette. An electrical circuit includes photoemissive and photosensitive means such as a photoemitter and photodetector, wherein the photoemissive means is in intimate optical contact with the first ray modifying optical element of the cuvette and wherein the photosensitive means is in optical contact with the second ray modifying means.
U.S. Pat. No. 4,193,692, which issued to Wynn on Mar. 18, 1980 describes a method and apparatus for the optical measurement of the concentration of a particulate in a fluid. An optical concentration measuring apparatus and method which provides an output signal which is a substantially linear function of the concentration is disclosed in the Wynn patent. The apparatus includes a chamber for containing a fluid sample and a source of optical radiation which develops a beam which is transmitted through the chamber and through the sample. A first photoelectric cell is disposed to receive the transmitted beam for generating an electrical signal commensurate with the intensity of the beam after passage through the chamber and the fluid sample. A second photoelectric cell which is disposed at a selected angle with respect to the direct beam for providing an electric signal commensurate with the light scattered in a direction corresponding to the selected signal is also provided. The signal commensurate with the scattered beam and the signal commensurate with the direct beam are applied to a single processor which develops a ratio of these signals. One of the signals is multiplied by a constant value. The method allows the constant value to be selected so that a signal from the signal processor is substantially linear with the particulate concentration.
Known turbidity sensing devices operate under one of two conditions. First, a tubular structure is provided to cause a fluid to flow past a predetermined detection zone. As the fluid flows through the conduit, a light is directed through the fluid and received by one or more light sensitive components disposed across the diameter of the conduit and, occasionally, at an angle to the line extending between the light emitting means and the light sensitive component which is disposed on an opposite side of the conduit from the light emitting means. An alternative method of utilizing a turbidity sensor is to provide a fluid connection tank, or well, which contains a sample portion of the fluid to be monitored. The light emitting and light sensitive components are arranged at sides of the well to direct a light through the fluid. Both of these known methods of applying a turbidity sensor have a common disadvantage. They require some means for directing or transporting fluid to the operative detection zone of the sensor. This requirement limits their adaptability in certain applications.
In addition to the disadvantage described above, known turbidity sensors are not easily adapted to incorporate a plurality of other sensors, such as a temperature sensor, a conductivity sensor and a position detector that permits the detection of movement of a preselected component, such as a rotatable washer arm. In modern apparatus for cleansing articles, such as dishwashers or clothes washers, the control circuitry can benefit from information relating to the turbidity of the washing fluid, the conductivity of the washing fluid, the temperature of the washing fluid and the movement of a rotatable member such as a water spray arm. It would therefore be beneficial if a single sensor module, or cluster, could be provided which is able to sense the turbidity, the temperature and the conductivity of the washing fluid and also determine whether or not a moveable object is properly functioning. It would be further beneficial if such a cluster of sensors could be provided as a single item which is disposable in a multiplicity of locations within the appliance without the need for providing tubing, conduits or fluid containing reservoirs. It would also be beneficial if a cluster of sensors could monitor the parameters of a device, such as its temperature, water turbidity level, water conductivity level and the position of a moveable object, in parallel with the control of an appliance by another microprocessor and make the measurements of the parameters available on call by the other host microprocessor. In this way, the host microprocessor would not be burdened by the necessity of waiting while the measurements were taken.